1. Field
This invention pertains to lights of the type in which a light source is focused through a lens to produce a concentrated spot of light on the work area. It is particularly directed to an improved diffusion lens element for such lights and provides such a lens element which is especially useful in connection with surgical lights.
2. State of the Art
Lights have long been available in which a light source is focused through a light path region of a lens element to produce a concentrated spot of light on a work area. Exemplary of such lights are those which are used by surgeons to illuminate an operative sight. Typical such surgical lights are disclosed, for example, by U.S. Pat. Nos. 3,005,087; 3,588,488; 3,887,801; 4,196,460; and 4,380,794 the disclosures of which are incorporated by reference as a part of this disclosure for their teachings concerning the general structure and operation of such lights as well as the general construction and arrangement of light cover lenses and the optical design of such lenses.
An important design criterion and objective in the design of surgical lights and the cover lenses incorporated in such lights is the ability to produce a concentrated spot of light which is of uniform intensity gradation "center-to-edge." Light patterns resulting from irregularities in the reflector and/or lamp assemblies housed by the light opposite the lens from the work site are distracting. Various expedients have been suggested for smoothing the light pattern produced by surgical lights. It has become conventional practice to lightly frost one or both surfaces of the cover lens for example. Various honeycombed or other light-diffusing surface textures have also been attempted. Such lens surface treatments constitute means both for smoothing the light pattern and for disrupting a direct view of the internal components of the surgical light, a view which is also distracting and aesthetically displeasing.
The techniques adopted in the lighting art for smoothing the light pattern and for obstructing a direct view of the internal components of the light have generally been accompanied by a reduction in efficiency (reduced light transmission and/or increased light scatter). Moreover, the surface characteristics of currently available cover lenses are not closely defined, being largely subjective. Thus, it is difficult to manufacture such cover lenses with consistent optical properties.